Rake receivers are widely used for demodulating signals transmitted in code division multiple access (CDMA) communication systems. The rake receiver is effective for demodulating signals which are subject to interference caused by multipath interference.
A rake receiver is utilized to despread transmissions received from a transmitter through utilization of a cross correlator and a code generator, as is conventional. The rake receiver receives both direct, (i.e. line of sight), RF waves as well as delayed, (i.e. multipath), RF waves due to different transmission path lengths, reflections, etc. Since the direct RF wave is not necessarily the strongest signal or is often not strong enough for reception, synthesizing, (i.e. combining), the energy of the direct RF waves with the energy of delayed waves results in better signal reception.
Each finger of a rake receiver is provided with a plurality of cross-correlators and co-generators for performing despreading. Time offset is adjusted using a delay circuit whereupon all the signals are added together after imposing the appropriate delays to these signals.